The present invention generally relates to the field of electronic devices, particularly computer systems, network servers, and the like having an expansion bay employing expansion cards, and particularly to an EMI shield for ports providing access to expansion cards within such electronic devices.
Electronic devices, particularly, computer systems, network servers, photocopiers, facsimile machines, printers, control equipment, medical equipment, telecommunication equipment, and the like often employ expansion or interface cards providing expansion of functions for the electronic device or extending the ability of the device to communicate with and/or control peripheral devices, networks or the like. Such expansion cards typically comprise generally rectangular printed circuit boards having an edge connector formed along one side edge. The edge connector is inserted into an expansion slot disposed on a system board (often referred to in the art as a motherboard) mounted within the electronic device to couple the installed expansion card to other electronic components in the device. In typical configurations, the expansion slots are oriented so the expansion cards installed therein are arranged in a spaced apart, generally parallel array wherein end edges of the cards are aligned with each other.
Extending along the aligned end edges of the expansion cards are metal mounting brackets having outwardly bent tabs positioned adjacent to the side edges of the cards opposite the edge connector. When the expansion cards are installed within the chassis of the electronic device and seated in the expansion slot, these tabs rest against a ledge surface formed inside the chassis. Ports are formed within the chassis to provide access to expansion cards received therein via connectors, controls and the like disposed on the mounting brackets.
Because these ports form an opening in the chassis of the electronic device, shielding must be provided to prevent Electromagnetic Interference (EMI). Such shielding typically comprises one or more stamped metal gaskets attached to the chassis of the electronic device around each port. Fingers are formed in the gasket adjacent to the port openings to improve electrical contact between the mounting bracket of the expansion card and the housing for shielding the electronic device from EMI.
In the past, the use EMI shielding employing stamped metal gaskets has been problematic. For instance, where multiple cards are installed in an expansion bay, the pressure exerted by the installation of a first card often causes the gasket to flex or bend making later installation of cards in adjacent ports more difficult. Moreover, fingers formed in the gaskets typically comprised a small tab that is detached from the gasket at one end. These fingers may bind against the expansion card bracket as the expansion card is inserted, preventing the card from being properly seated. Further, because of their shape, fingers employed by conventional gaskets provide poor grounding between the expansion card bracket and the housing of the electronic device, and are thus not effective at reducing EMI.
Consequently, it would be desirable to provide an improved EMI shield which does not flex allowing two or more expansion cards to be inserted within adjacent expansion slots with uniform pressure, and which includes fingers that do not cause the expansion card bracket to bind as the expansion card is inserted within an expansion slot. The EMI shield should provide good EMI grounding between the brackets of expansion cards inserted in expansion slots (or alternately, between expansion port covers where no expansion card is used) and the chassis of the electronic device.
Accordingly, the present invention is directed to an EMI shield for ports providing access to expansion cards received in the chassis of an electronic device. In an exemplary embodiment, the EMI shield comprises a gasket suitable for being disposed between the chassis of the electronic device and the expansion card bracket. The gasket includes an aperture overlying each of the ports and a plurality of generally flattened U shape fingers formed in the gasket adjacent to each aperture for engaging the bracket to provide EMI grounding between the bracket and the chassis.
Preferably, the gasket is shaped so that flexing of the EMI shield is limited, allowing two or more expansion cards to be inserted within adjacent expansion slots with uniform pressure. Moreover, the fingers reduce binding between the expansion card bracket and the gasket as the expansion card is inserted within an expansion slot. The fingers also allow the EMI shield to provide good EMI grounding between the brackets of expansion cards inserted in expansion slots (or, alternately, between expansion port covers where no expansion card is used) and the chassis of the electronic device.